docs: def _flush_graph_val(self):
          """Send all new and changed graph values to the database."""
          if not self._graphvals2set:
              return
          delafter = {}
          for graph, key, branch, turn, tick, value in self._graphvals2set:
              if (graph, key, branch) in delafter:
                  delafter[graph, key, branch] = min((
                      (turn, tick),
                      delafter[graph, key, branch]
                  ))
              else:
                  delafter[graph, key, branch] = (turn, tick)
          self.sqlmany(
              'del_graph_val_after',
              *((graph, key, branch, turn, turn, tick)
                for ((graph, key, branch), (turn, tick)) in delafter.items())
          )
          self.sqlmany('graph_val_insert', *self._graphvals2set)
          self._graphvals2set = []